Automatic control for burst firing



Dec. 5, 1950 c. A. s. TEECE AUTOMATIC coNTRoL FOR BURST FTRTNG 2 sheets-sheet 1 Filed March 27, 1946 INVENTOR.

2 Sheets-Sheet 2 INVENTOR. BY Cc/ f7/356i c. A. s. TEEcE AUTOMATIC CONTROL ,FOR BURST FIRING Dec. 5, 1950 Filed March 27. 1946 Patented Dec. 5, 1950 2,532,794 AUTOMATIC CONTROL FOR BURST FIRING Cecil Auburn Selwyn Teece, Barton, Canberra, Australia Application March 27, 1946, Serial No. 657,383 In Australia April 5, 1945 Claims.

invention relates to automatic firearms including automatic rifles, machine guns, light machine guns, and so called sub-machine guns, and has particular, but not necessary limiting, reference to such rearms which operate on the blow-back principle.

Hitherto, interruption of continuous ring has been dependent upon manual release of the firing trigger. Military operations, however, have proved that, on account of the high rate of re, manual control is quite inadequate and that serious wastage of ammunition occurs leading to combat troops becoming devoid of ammunition at vital or critical periods.

With a view to conserving ammunition 'under combat conditions, attempts have been made to reduce the rate of fire of automatic firearms, the objective being to interrupt continuous ring by manual release of the trigger after a relatively small number of cartridges has been discharged. According to one proposal of such a character, it has been suggested to slow down the rate of re by deliberately increasing the weight of a part or parts of the action.

Such proposals, While they may facilitate conservation of ammunition, are actually retrograde in principle and in result, primarily in that they sacrifice the beneficial results which accrue from an optimum high rate of nre. Thus, reduction of the rate of re, below the optimum for any particular automatic rearm, inevitably impairs the accuracy of a continuous cone of lire. In this connection it may be taken as established that the optimum cyclical rate of fire of practically any automatic iirearm, in order to obtain maximum accuracy in continuous fire, is so high as to render it physically impossible for the trigger to be manually released with such speed and precision as to ensure that only a predetermined and relatively small number of cartridges will be discharged in a burst of continuous re.

It will be apparent from the foregoing that in lendeavouring to achieve the objective of conserving ammunition by reducing the rate of re in order that the continuous lire may be effectually arrested after a particular number of cartridges has been discharged, conditions have been established in the rate of iire Which are detrimental to the achievement of maximum accuracy during continuous lire.

The primary object of this invention is to provide simple, practical and reliable means for reconciling these two hitherto incompatible conditions. whereby ammunition may be conserved and, at the same time, the optimum rate of nre may be adopted for accuracy of the trajectory of any particular rearm.

With that object in View, the invention eliminates the necessity for manual manipulation of the trigger in order to arrest continuous lire, and provides for the interposition between the trigger mechanism and the action of the firearm of an automatic control device which is adapted to be intermittently actuated directly by the action in order that, irrespective of the rate of re, the trigger mechanism will automatically arrest firing immediately after a predetermined number of cartridges has 'been discharged in a burst of continuous firing. The control device is of such form and is so co-ordinated with the action as to be positive and denite in operation and is locked in a stationary condition after each intermittent actuation by direct physical contact with the action.

Thus with the inventio control of continuous firing (i. e. the number of cartridges discharged during a burst of continuous fire) is taken out of the hands of the marksman but he may, by normal manipulation of the trigger, discharge series of the predetermined relatively short bursts in rapid succession whenever so desired.

Provision may be made whereby the marksman may also cause firing to be automatically interrupted after each shot, or throw the control device out of operation so that true or unlimited continuous ririg may be achieved.

From the foregoing and from the description to follow, it will be apparent that a control device for automatic firearms is provided which, by

virtue of being constrained in its intermittent actuation, is capable of functioning in an automatic firearm having a very high cyclical rate of lire. As previously stated, every automatic firearm has an optimum cyclical rate of lire for the best grouping of shots under continuous ring conditions. This optimum rate of iire, however, is very much higher, especially in automatic lirearms of the sub-machine gun type, than is acceptable to military authorities with manual con trol of continuous iiring conditions.

' It is accordingly possible, with the realization of this invention, to raise the cyclical rate of lire to the optimum rate referred to for any particular automatic rearm, in consequence of the fact that there is available, according to said invention, an automatic control device which positively interrupts the firing after a predetermined number of shots has been discharged under continuous ring conditions for each pressure of the trigger.

Among the factors which determine the cyclical rate of fire of an automatic firearm operating on the blow-bac principle is, in addition to the weight and stroke of the bolt, both of which may be reduced, the diierence in spring pressure aoting upon the bolt when the bolt is in the closed position and when it is at its extreme rearward position. The adoption vof a single spring system exerting the requisite -high pressure on the bolt necessitates excessive and objectionable manual pressure on the cooking handle during manual cooking of the bolt.

Therefore as a further feature of the invention, which will enable full advantage-to .be derived from the ability to raise the cyclical rate of re to the optimum Value while permitting of controlled continuous firing, I contemplate -employing, in combination with a control device as aforesaid, a duplex spring arrangement, itself of known or any suitablelform, in which a first or relatively lightsspring yieldingly opposesfrearward movement of a reciprocatingboltpr like-action Afor a substantial distance -from the .bolt closed position-anda second or relatively vheavy spring ,which uponbeingompressed byV continued rrear- `ward movementfof the-:bolt-intoits extremezrearward position exerts a greatly increased pressure on the bolt.

The foregoing and other objects and advantages of the -invention will become readily apparent -from thefollnwing description and-annexed-draw- -ings which relate, Joy way of .'example, to V an `adaptaton;rif-.the inventiongtofa -s-ub -machine-gun .pf welllknown typewhich-embodiesEa-rreciprocat- :ingbolt action and loperates-onthefbloweback f principle. It -is .-tosbe understoodthat-thednvention is .not `limited to such a ggun -or -to-:gunsoperating -npon the fblow.back principle.

In the drawings:

`Figure 1 is a Iside. elevation, vpartly in section, offthe essential parts, of a -sub-machine gun incor- :poratingacontreldevice according to one -form of the'invention. The parts are shown in a condition ready tocommenoe a burst of .continuous re.

Figure 2 shows the relevant parts after the triggerhas been pressed to initiate .-ring.

Figure 3 shows `the parts after the rst-shot has :been fired and-the bolt is returning ,under `recoil.

Figure 4 shows a -furt-her vstage in the recoil movement of the bolt which has reached the stage where it engages the control device and commences toturn it.

`Figure 5 shows the parts after the last round of a burst has been fired, the control device being about to act upon the trigger mechanism in order to restore it to the normal position,ready to arrest continuous fire and to initiate another burst of ring.

Figure 6 is a diagram indicating how adustments 'may be made to permit of single shot ring Vor complete continuous ring.

Figure 7 is a face view of a rotary control member suitable for bursts of three shots.

Figure 8 is a diagram similar to Figure '6 but Vapplicable to the control member of Figure '7.

According-to Figures 1 to 6, the control-de- -Vice-comprisesa rotary member 2 in the-form of a cam or plate of approximately square shape having its perimeter -constituted by the Vstraight edges ABCD Y each of -which is recessed near one end soas to produce abutment faces a, b, c, dat the respective corners A,of-theplate. 'The member 2 1s also provided at or near its perimeter .with

a laterally projecting lobe or striker 4. The memy ber 2 may be fast upon a spindle 6 which extends transversely beneath the firearm action, e. g. the reciprocating bolt '1, the spindle being rotatably supported, as by bearings (not shown) in the trigger guard or other convenient part.

The bolt I may be oi ani! appropriate deSigl and construction but according'to the illustrated form of the invention -is provided in its under surface and toward its rear with a recess 8 in 1on- Vgitudinal alignment with the rotary member E, the recess being ,curved as shown or of other suitable shape and depth as will enable member 2 to turn :partly 'into the recess S as the latter comes into registry with the upper forward corner of member 2. The recess terminates at its forward end in a shoulder 9 for co-operation with the abutment faces a, b, c, d of member 2 as will be described hereinafter.

The bolt is provided with the usual inclined :facefor bent Vit `to be engaged Aby an extremity of the-Sear 1I,'hereinvexemplied as a bell-crank' lever pivotedfat II2 and (zo-operating with va-step I'3a-formedintermediately ofthe length of ccnnector I 3 :the-rear'fendmf 'which Vis pivoted at I4 to the upper part of the trigger-l5 which-is pivoted at 16. .'Ihe fforwardrend I3?) ofthe `connector xtendsfbeyondfthe Ysear and is disposed inthe path of thezstriker 5f on the'rotary member 2.

The :trigger Tspring II is shown -connected at its `rear nenel,v 'to `vthe trigger and at :its forward en'dftoa drat .trap-spring I8 :encircling a pin I9 outstanding from the lower end ofthe lsear,'the free aand i-'pofrtion Ifa oi `the -spring extending vtransversely*beneath the connector 'I3 in Iorder vto yieldingly urge it upwards about pivot IA.

.Abiassingfspringz is vshown :acting upon the rotarymember 2 -in order to turn'it initially 'as soon as-the recess "Binthe undersurfaceoi the boltcomesdnto registry with the upper :forward -cornenportion of'the rotary-member.

Inl-.Figure 1,'the parts-areshown in position ready to commence a :burst-of continuous fire, which, in the present'case, will consist of four shots. It `will benoted that edge 'A of'the'rotary member `2 is in linear-contact with lthe under surface of thebolt so that member! is at the moment locked against rotation.

Upon pressing the trigger, `the connector t3 by its forward movement-swings the scar I I about its pivot I2, thus releasing the'bolt-'I' for'the-rst shot. When'the forwardly travellingibolt reaches the position shown in V'Figure f2, the .biassing spring .213 automatically -tinns member 2 in the v'direction of the arrow anci'locks it by co-operation of the ystraight edge of `the spring with the fiat edge of the member-2 asin Figure 3, so that its corner portion enters the bolt recess' and thus brings abutment face a into position I-to beengage-:l lby the shoulder -S Aat `the forward end of the bolt recess '8 during return -orrecoil of the bolt which is assumed to have commenced -in Figure 3.

Figure 4 depicts a further stage of the recoil movement from which it will be apparentthat as the bolt continues its recoil movement, member 2willlbe=turne by the engagement of shoulder 9 with face a until it has completed one-quarter of a revolution from the initial position. Thereby edge VB is brought into contact with the under surface of the Abolt and arrests the member 2' when its -angular momentum -is greatest, and locks :it-against further rotation.

gisthe Sear il remains retracted from the bent I0, the bolt continues its reciprocating motion to re three additional shots. During that phase, movements similar to those described in relation to Figures 2, 3 and 4 are repeated with the exception that it is the edges C, D and A which are successively brought into contact with the under surface of the bolt. During the recoil of the bolt after the fourth or final shot, the striker l! on member 2 engages the forward end 13b of the connector, as indicated in 'Figure 5, swinging it downwardly about its pivot. This releases the sear H for swinging movement under influence of spring I8, with the result that the sea-r engages the bent I0 and arrests firing.

Upon relaxing pressure on the trigger the gun is ready for a further burst of continuous fire.

It will be appreciated that the control afforded by the invention is most positive and denite, due primarily to the fact that the control member 2 is directly operated by the firearm action (e. g. the reciprocating bolt) and also, because at all periods, other than when the control member is under forced and deliberate motion, it is positively locked against movement by physical contact with the firearm action, consequently there is no possibility of backlash or other undesired or inadvertent movement of the control device which might interfere with its eflicient, reliable and precise controlling function.

It will also be apparent that, on account of its direct action and self-locking properties, the control device can be of the utmost simplicity and compactness and be made suiciently robust as to withstand prolonged and hard use.

As previously mentioned the embodiment of Figures 1 to 6 provides for burst of four shots but by providing member 2 with another striker diametrically opposite the striker the bursts would be limited to two shots.

Should it be desired to provide for three shot bursts then the control member may be of generally triangular shape as seen in Figure '7.

The control device also lends itself to adjustment in order that single shot and true continuous fire may be obtained whenever so desired.

For this purpose a spring influenced plunger or press button of a kind well known in the art may be associated with the connector I3 to enable it to be displaced laterally in relation to the rotary member 2. Thus referring to Figure 6, with the connector in the unbroken line position four-shot or two-shot bursts will be obtained depending upon whether one or two strikers 4 are provided, in the dot-dash line position only single shots would be possible while in the dotted line position continuous re interrupted only by manual release of the trigger would be obtainable.

Similar remarks apply to the three-shot control device of Figure '7 as will be apparent from Figure 8 without further description.

In order that full advantage may be taken in the application of the present invention to an automatic firearm by way of raising the cyclical rate therein to the optimum value referred to hereinbefore, a duplex spring system as illustrated in Figure 1 cf the drawings may be adopted. In this spring system, the spring S controls the bolt movement between the bolt closed position and slightly rearward of the position at which the sear l I engages with the bent IB, after which the tailpiece T of the bolt 'I abuts against the washer W interposed between the spring S and the heavier spring HS, which then yieldingly opposes further rearward movement of the bolt,

and in doing so imposes a much higher pressure 6 thereon for any given further rearward movement of the bolt.

By means of this duplex spring arrangement the pressure which must be exerted on the cocking handle to cock the bolt is only dependent upon the compression `of the spring S, whereas the pressure exerted on the spring HS by the tailpiece T upon contacting the washer W causes the spring HS to exert a very much increased spring pressure on the bolt than that exerted by the spring S, the maximum value of which is the primary factor in determining the cyclical rate of fire.

It will be understood that while according to the exemplification of the invention as illustrated in the drawings the rearward face of the bolt constituting part of the action actuates the polygonally shaped cam, such cam may be arranged so as to be actuated by the forward end of the bolt or by any suitably positioned member.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. In an automatic firearm, the combination with an action and a trigger mechanism of a control device including a straight edged cam member, an axle member extending transversely of said action and about which said cam member is mounted to turn, said cam member being intermittently turned about said axle by engagement of said action while moving in one direction in order to ensure that said trigger mechanism will automatically arrest firing immediately after a predetermined number of cartridges has been discharged in a burst of continuous firing, said control device being positively constrained from movement immediately after each intermittent actuation by one of its edges being brought into contact with a surface of said action, means for biasing said control device so as to initially turn the same into operative position in relation to said action after said action has completed each forward movement thereof, said control device comprising a rotary member having a perimeter constituted by a series of angularly related edges, an abutment face between each adjacent two of said edges, and an outstanding striker, the rotary member being so mounted and disposed as to be repeatedly and intermittently turned by direct contact of a member of the firearm action with the successive abutment faces during a burst of continuous iiring, whereby said edges are successively brought into linear engagement with said action member between each turning motion of the rotary member in order to lock the latter against undesired turning, said striker after at least two successive turning motions of the rotary member, engaging in element of the trigger mechanism to restore it to an operative condition which arrests continuous ring.

2. In an automatic firearm, the combination with an action and a trigger mechanism of .a control device including a straight edged cam member, an axle member extending transversely cf said action and about which said cam member is mounted to turn, said cam member being intermittently turned about said axle by engagement of said action while moving in one direction in order to ensure that said trigger mechanism will automatically arrest ring immediately after a predetermined number 'of cartridges has been discharged in a burst of continuous firing, said control device being positively constrained from movement immediately after each intermittent actuation by one of its edges being brought into ycontact with a surface of said action, means for biasing said control device so as to initially turn the same into operative position in relation to said action after said action has completed each forward movement thereof, said control device comprising a control member having a perimeter constituted by a series of substantially straight edges,V an abutment face at or near each of the respective corners,v and a striker adjacent the perimeter, said control member being rotatably mounted in juxtaposition to the firearm action, and the latter being provided with a formation for successively engaging said abutment faces, whereby during a burst of continuous firing the control member will: be intermittently turned to eventually cause said striker to engage an elementof the triggefmechanism and restore it to a condition to arrest the continuous fire, said straight edges of the control member being successively brought into lineal contact with a lineal surface of' said action as a result of and immediately after each turning motion of the control member so that the latter is prevented from turning about its axle until it is again turned by movement of said action'.

3. In an automatic firearm', thev combination with. a reciprocating' action and a trigger mechanism, of a. dev-ice'for controlling continuous iiringcomprising acontrolmember having a perimeter constituted by at least three substantially straight edges and provided with an abutment face at or near each` corner, and with a laterally projecting striker' adjacent its perimeter, said control. member being rotatably mounted about anf axis-extending in' a plane normal to the axis of said reciprocating action, said action being provided with a' shoulder for. engagement with said abutment faces, whereby during a burst of continuous ring the control member will beintermittently turned by the reciprocating action untilsuch striker is caused' to engage said trigger mechanism and restore it to a condition to arrest continuous re, said edges of the control member being successively brought into lineal contact with saidaction immediately after each turning motion of the control member in order toY maintain the latter stationary pending its nent turning motion, and means for biasing said control member so as to initially turn the same into operative position in relation to said action after said action has completed each forward movement thereof.

4. In an automatic'rearm accordingto claim 3; wherein said control member is disposed beneath s aid reciprocating action so that said edges ofthe control member engage the under surface of said action.

5. InA an automatic firearm according to claim 3; wherein said reciprocating action is provided at a position in longitudinal alignment with said control member with a recess to enable the corner portions of said control member to enter said recess during the intermittent turning 'motions ofthe control member, said recess terminating at one end in said shoulder for engaging said abutment faces;

6. In an automatic rearm, the combination with a reciprocating bolt having a bent and a trigger mechanism adapted to actuate a sear for co-operating with said bent, of a device for controlling continuous firing, comprising a controlv member having substantially straight-edges', means for rotatably mounting said control mem'- berfaboutan axis extendingv transversely o f said bolt so that said edges may make lineal contact with a surface of said bolt in a lengthwise direction thereof, abutment faces located one adjacent each corner of said control member, a shoulder formation on said bolt for successively engaging said abutment faces during recoil of said bolt thereby intermittently to turn said control member, a striker outstanding from said control member, a connector extending between said trigger mechanism and said Sear and having a portion disposed in the path of said striker, and means for biasing said control member so asto initially turn the same into operative position in relation to said action after said action has completed each forward movement thereof.

7. In an automatic firearm, the combination with a reciprocating action and a trigger mechanism, of a device for controlling continuous nring comprising a control member having a perlineter constituted by at least three substantially straight edges and provided with an abutment face at or near each corner, and with a laterally projecting striker adjacent its perimeter, said control member being rotatably mounted about an axis extending in a' plane normal to the axis of said reciprocating action, said action being provided with a shoulder for engagement with said abutment faces, whereby during a burst of continuous firing the control member will be' intermittently turned by the reciprocating action until such striker is caused to' engage saidtrigger mechanism and restore it to a condition to arrest continuous fire, said edges of the control member :being successively brought into lineal contact with said action immediately after each turning motion of the control member in order to maintain the latter stationary pending its' next turning motion, and a spring arranged to initiate each intermittent turning action of said control member.

8. In an automatic firearm, the combination with a reciprocating action and a trigger mechanism of a control device including a straight edged cam member, mounted to turn about an axis extending transversely of said action, means associated with said cam member intermittently engageable by said action whereby said cam member is intermittently turned about said axis during movement of the action in one direction, further means associated with said cani member adapted to engage an clement of said trigger mechanism to ensure that said trigger mechanism will automatically arrest ring immediately after a predetermined number of cartridges has been discharged in a burst of continuous firing, said control device being positively constrained from movement immediately after each intermittent actuation by one of its edges being brought into linear contact with a surface o'f said action, and means for biasing saidY control device so as to initially turnthe same into operative position' in relation to said action after said action has completed its said movement in one direction.

9. In an automatic firearm, the combination with an action and a trigger mechanism of a control device, said control device comprising a rotary member having a perimeter constituted by a series of angularly related edges, an abutment face between each adjacent two of said edges, and a, striker outstanding from the perimeter, the rotary member being so mounted and disposed' as to berepeatedly and intermittently turned by Vdi're'ct'-c'xitactof a member of the firearm-action with the successive abutment faces during a burst of continuous ring, intermittent turning of said rotary member bringing successive edges of said latter member into lineal contact with said action member said lineal contact locking said rotary element against undesired turning between each turning motion; said striker after at least two successive turning motions of the rotary member, engaging an element of the trigger mechanism to restore it to an operative condition to arrest continuous ring.

10. In an automatic firearm, the combination with an action and a trigger mechanism of a control device, said control device comprising a control member having a perimeter constituted by a series of substantially straight edges, an abutment face at or near each of the respective corners, and a, striker adjacent the perimeter, said control member being rotatably mounted in juxtaposition to the firearm action, and the latter being provided with a formation for successively engaging said abutment faces, whereby during a burst of continuous firing the control member will be intermittently turned to eventui 10 ally cause said striker to engage an element of the trigger mechanism and restore it to a condition to arrest the continuous fire, intermittent turning of said control member bringing successive straight edges into lineal contact with a surface on said action member to lock said rotary member against undesired turning pending its next turning motion.

CECIL AUBURN SELWYN TEECE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,484,163 Vincon Feb. 19, 1924 2,361,180 Dobremysl Oct. 24, 1944 FOREIGN PATENTS Number Country Date 314,767 Germany Oct. 8, 1919 

